1. Field of the Invention
The invention relates to a spring drive device, more particularly to a spring drive device for a sunshade assembly.
2. Description of the Related Art
A sunshade assembly generally comprises a pair of spaced-apart mounting seats, a winding shaft connected rotatably to the mounting seats, and a shade member wound on and having one end connected to the winding shaft. One of the mounting seats includes a spring member disposed therein. The spring member has one end secured to the one of the mounting seats, and an opposite end connected to the winding shaft. When the shade member is unwound, the winding shaft rotates to twist the spring member, so that the winding shaft can rotate stably under a restoring force of the spring member. In addition, before being assembled to the respective mounting seat, the spring member is twisted so as to have a restoring force stored therein, such that the shade member can be tightly stretched when being unwound, even in the case where the extent of unwinding of the shade member is minimal.
U.S. Pat. No. 7,694,712 B2 discloses a conventional spring drive assembly of a sunshade. The conventional spring drive assembly comprises a coil spring and a coupling shaft. The coupling shaft has one end connected co-rotatably to a winding shaft via a bushing, and an opposite end engaging separably an end segment of the coil spring. As such, when the winding shaft is rotated, the spring member will simultaneously be twisted. A securing pin and a spring clip are provided to prevent the coupling shaft from moving longitudinally, thereby maintaining the engagement between the coupling shaft and the spring member.